I started with Kicad because it's open source but I soon became aware that Eagle seems to be the "defacto" standard for most DIY projects found on the web. Being a newbie at electronics I often try to find a circuit design I can adapt to my needs. Doing this also has the advantage of being able to get a feel for layout design.There are also a large number of tutorials for Eagle that I've found very useful. And I haven't yet exceeded the size limit.

Couldn't get used to Eagle, using DipTrace nowadays and trying to get into KiCad (according to Laen from OSHPark--formerly called the DorkbotPDX PCB service--KiCad has overtaken Eagle in popularity with hobbyists submitting boards to his service)